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Katrina’s effect on waterfowl both good and bad

Oct 31, 2006

As the human residents continue to rebuild after last year’s Hurricane Rita, feathered visitors to southwest Louisiana will find a bounty of food resources this winter. Biologists with Ducks Unlimited believe the annual plant growth that occurred in the marshes and wetlands this spring and summer will support large populations of wintering waterfowl.

“It is astonishing to see the amount of natural seed that is out there for the ducks this year,” said DU regional biologist Chad Courville.

According to Courville, disturbance caused by hurricanes and other natural events, like fire, are part of the system that keeps the marshes in southern Louisiana healthy. Healthy marshes are interspersed with patches of open water and thick stands of grasses and emergent vegetation. Over time, marsh vegetation becomes dense, eventually eliminating the open water patches in the marsh. This “closed marsh” situation is not productive and has little value to waterfowl and other wildlife.

“Strictly in terms of waterfowl habitat, Katrina and Rita had both good and bad effects,” said Tom Moorman, director of conservation planning at DU’s southern regional office. “On one hand, a recent report from the U.S. Geological Survey’s National Wetlands Research Center suggests the storms caused significant transformation of coastal lands to open water.

“On the other hand, the flooding of the closed marsh with salt water from the storm surges set back plant succession and reinvigorated large areas of marsh. So, while the storms caused some direct habitat losses, they also improved the quality of some areas in terms of waterfowl food production.”

Many of the marshes on Cameron Prairie National Wildlife Refuge were in a closed marsh state before Hurricane Rita. “When the saltwater flooded these marshes, it killed most of the maidencane that was choking the system,” said Glenn Harris, refuge manager. “Once it started raining here and the marshes got a flush of freshwater, the annual grasses and sedges that are more beneficial to waterfowl began to grow.”

Moorman noted that in mid-September, early migrating blue-winged teal and northern shovelers were already feasting on the foods available in the marshes that rebounded from the hurricane disturbance. Mottled ducks and whistling ducks were also taking advantage of the new flush of resources.

“Historically, hurricanes have been a significant force in shaping the complex ecology of the Louisiana coast. Today, with alterations to the system’s hydrology, hurricanes can cause significant habitat loss. Ultimately, the system needs to be restored to a point where marsh creation by natural processes is more or less in equilibrium with marsh loss.”